PTL 1 discloses a configuration that is provided with a selective catalytic reduction (SCR) catalyst, an adding valve which adds urea water to exhaust gas flowing into the SCR catalyst, and a low-pressure EGR system which guides some of the exhaust gas (exhaust gas recirculation (EGR) gas) to an intake passage from an exhaust passage further downstream than the SCR catalyst.
PTL 2 discloses a configuration in which a spark ignition-type internal combustion engine is provided with a device that supplies ammonia to an intake passage and an SCR catalyst that is placed in an exhaust passage.